The science of attraction


By James Emery, SciTech Deputy Editor and Sarah Dalton, SciTech Editor

Is your Briscrush a declaration of love or just a biological response? This Valentine's day, SciTech explores the many scientific theories that have attempted to explain attraction

Sexual attraction between humans is very complex and is influenced by a wide range of factors including our environment, the society we’ve been brought up in and of course our biology. Due to this complexity, it is hard to pinpoint exact scientific reasons for why you are attracted to some humans and not others.

However, it seems that most of the biological factors that impact how attractive we find someone are related to passing on our genes with the best mate to produce the strongest offspring possible (romantic, I know!).

The biological factor with the most evidence supporting its role in attraction is the major histocompatibility complex (MHC) otherwise known as the human leukocyte antigen. The primary function of the MHC is within the immune system where they act as self-markers on the surface of your cells to help your immune system know that they’re not a foreign body that needs to be attacked.

Most of the biological factors that impact how attractive we find someone are related to passing on our genes | Epigram/James Emery

However, it has recently been shown that the genetics of your MHC complex could have a role in determining who you find attractive. The way that animals can sense whether a potential partners MHC is similar or different to their own is through scent, with the natural odour of someone with a differing MHC smelling better than someone with a similar one.

Multiple animal studies have found that when given a choice between a mate which has a similar MHC and one that has a differing one, they prefer the mate which differs. This is because it is evolutionarily advantageous to breed with a mate that has a differing MHC to your own as it will give your offspring more varied MHC genes and thus a stronger and more adaptable immune system.

This phenomenon has also been seen in human studies which found that people that were partnered with someone with a differing MHC were more satisfied with the relationship, their sex life, and wished to have (more) children with them.  

While our base biology plays a role in attraction, what we find to be attractive is also dependent on environmental and societal factors

Another big biological influence is the perceived fertility of the person, with those that are more fertile being seen as more attractive, which again buys into the idea of finding the best mate to pass on your genes to the next generation. Studies have shown that men find the scent of women with higher levels of oestrogen and lower levels of progesterone, which is an indicator of female fertility, to be more appealing. Women with this hormone balance were also rated to have more attractive faces and voices by men.

This also goes the other way, with women finding more masculine features, and therefore high virility, on men to be more attractive but only when they are ovulating. When not ovulating or on the pill women in scientific studies tend to find more feminine features on men attractive.

However, the simplification of human sexual attraction to this basic biological level doesn’t really capture the complexity of it, especially when most of it is about finding the right person to breed with. These biological explanations fail to explain same-sex attraction in humans, where the factors of fertility and virility, as well as finding the best partner to produce a healthy child with, are basically irrelevant.

So, while our base biology definitely plays a role in attraction, humans are intelligent and complex, and what we find attractive is also dependent on environmental and societal factors.

There are many 'nurture' explanations to attraction in addition to those which place emphasis on our 'nature'. One of these which is widely accepted, is the psychological theory of self disclosure, based on the social penetration theory. This theory places an emphasis on the initial interactions with a person that extend beyond the physical, stating quite simply that the more you feel that a person is opening up to you about themselves, the more likely you are to be attracted to them.

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This gradual process of revealing your inner self must be a reciprocal exchange in order to build trust.

In a study of dating heterosexual couples, researchers found a strong positive correlation between attraction and self-disclosure in both partners, increasing intimacy, attraction and commitment. This is only one of the many theories used to explain the complex and yet everyday phenomenon of attraction.

Featured Image: Epigram/ Sarah Dalton

Do you think attraction is more to do with our biological nature or environmental factors?